U.S. patent number 11,005,147 [Application Number 16/481,273] was granted by the patent office on 2021-05-11 for pouch type secondary battery.
This patent grant is currently assigned to LG Chem, Ltd.. The grantee listed for this patent is LG CHEM, LTD.. Invention is credited to Seung Don Choi, Jong Pil Park.
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United States Patent |
11,005,147 |
Park , et al. |
May 11, 2021 |
Pouch type secondary battery
Abstract
A pouch type secondary battery includes: an electrode assembly
having an electrode including a positive electrode and a negative
electrode and a separator laminated therein; a battery case having
a pouch shape to accommodate the electrode assembly; an electrode
tab connected to the electrode and protruding from one side of the
electrode; a first electrode lead having one end connected to the
electrode tab; a second electrode lead having one end connected to
the other end of the first electrode lead and the other end
protruding to outside the battery case; and a connection part
bonding the first electrode lead to the second electrode lead to
connect the first and second electrode leads to each other, wherein
a first inclined surface is provided on at least one of the other
end of the first electrode lead and the one end of the second
electrode lead.
Inventors: |
Park; Jong Pil (Daejeon,
KR), Choi; Seung Don (Daejeon, KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
LG CHEM, LTD. |
Seoul |
N/A |
KR |
|
|
Assignee: |
LG Chem, Ltd. (Seoul,
KR)
|
Family
ID: |
1000005546160 |
Appl.
No.: |
16/481,273 |
Filed: |
August 9, 2018 |
PCT
Filed: |
August 09, 2018 |
PCT No.: |
PCT/KR2018/009136 |
371(c)(1),(2),(4) Date: |
July 26, 2019 |
PCT
Pub. No.: |
WO2019/045310 |
PCT
Pub. Date: |
March 07, 2019 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190379032 A1 |
Dec 12, 2019 |
|
Foreign Application Priority Data
|
|
|
|
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Aug 29, 2017 [KR] |
|
|
10-2017-0109443 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M
50/572 (20210101); H01M 50/172 (20210101); H01M
50/531 (20210101); H01M 50/124 (20210101) |
Current International
Class: |
H01M
50/572 (20210101); H01M 50/124 (20210101); H01M
50/172 (20210101); H01M 50/531 (20210101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
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H10-294097 |
|
Nov 1998 |
|
JP |
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2001-246590 |
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Sep 2001 |
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JP |
|
2011-076776 |
|
Apr 2011 |
|
JP |
|
2011-096664 |
|
May 2011 |
|
JP |
|
2016-085849 |
|
May 2016 |
|
JP |
|
10-2013-0014253 |
|
Feb 2013 |
|
KR |
|
10-2015-0034637 |
|
Apr 2015 |
|
KR |
|
10-2016-0049889 |
|
May 2016 |
|
KR |
|
10-2017-0004686 |
|
Jan 2017 |
|
KR |
|
10-1734703 |
|
May 2017 |
|
KR |
|
10-2018-0091324 |
|
Aug 2018 |
|
KR |
|
Other References
Office Action dated Sep. 7, 2020, issued in corresponding Japanese
Patent Application No. 2019-550192. Note: 2011-076776. cited by
applicant .
International Search Report dated Nov. 15, 2018, issued in
corresponding International Application No. PCT/KR2018/009136.
cited by applicant .
Communication dated Jan. 9, 2020, issued in corresponding Extended
European Search Report Application No. 18850290.0. Note: KR
2013-00449889. cited by applicant.
|
Primary Examiner: Slawski; Magali P
Assistant Examiner: Walls; Jessie L.
Attorney, Agent or Firm: Morgan, Lewis & Bockius LLP
Claims
The invention claimed is:
1. A pouch type secondary battery, comprising: an electrode
assembly comprising a positive electrode, a separator, and a
negative electrode layered such that the separator is between the
positive electrode and the negative electrode; a battery case
having a pouch shape to accommodate the electrode assembly therein;
an electrode tab connected to the electrode assembly and protruding
from one side of the electrode assembly; a first electrode lead
having one end connected to the electrode tab; a second electrode
lead having one end connected to the other end of the first
electrode lead and the other end protruding to an outside of the
battery case; a connection part bonding the first electrode lead to
the second electrode lead to connect the first and second electrode
leads to each other, and a step compensation part disposed on a
side of the other end of the first electrode lead, wherein a first
inclined surface is provided on at least one of the other end of
the first electrode lead and the one end of the second electrode
lead, wherein the step compensation part includes a plurality of
step compensation parts, wherein the first inclined surface is
provided on the other end of the first electrode lead, and each of
the plurality of step compensation parts has one end contacting the
first inclined surface in a state in which the plurality of step
compensation parts are laminated, and wherein the plurality of step
compensation parts increase in length in order of the lamination to
correspond to an inclined angle of the first inclined surface.
2. The pouch type secondary battery of claim 1, wherein the step
compensation part is integrally provided.
3. The pouch type secondary battery of claim 1, wherein the first
inclined surface is provided on the other end of the first
electrode lead, and a second inclined surface is provided on one
end of the step compensation part.
4. The pouch type secondary battery of claim 3, wherein the second
inclined surface has an inclination corresponding to the first
inclined surface.
5. The pouch type secondary battery of claim 3, wherein the second
inclined surface contacts the first inclined surface.
6. The pouch type secondary battery of claim 1, wherein the step
compensation part has non-conductivity is non-conductive.
7. The pouch type secondary battery of claim 1, wherein the step
compensation part has a thickness corresponding to the sum of a
thickness of the first electrode lead and a thickness of the
connection part.
8. The pouch type secondary battery of claim 1, wherein the first
inclined surface has an obtuse angle with respect to a bonding
surface on which the first electrode lead and the second electrode
lead are bonded to each other through the connection part.
9. The pouch type secondary battery of claim 1, further comprising
an insulation part surrounding a portion of each of the first and
second electrode leads to allow the first and second electrode
leads to be bonded to the battery case.
10. The pouch type secondary battery of claim 9, wherein a bonding
force between each of the first and second electrode leads and the
connection part is less than that between each of the first and
second electrode leads and the insulation part.
11. The pouch type secondary battery of claim 9, wherein the
insulation part surrounds a portion at which the first and second
electrode leads are connected to each other through the connection
part.
12. The pouch type secondary battery of claim 9, wherein the
insulation part includes at least one of a thermoplastic resin, a
thermosetting resin, and a photocurable resin.
13. The pouch type secondary battery of claim 1, wherein the
connection part includes a conductive polymer comprising a
conductive material.
14. The pouch type secondary battery of claim 1, wherein the
connection part has a thickness of 1 .mu.m to 500 .mu.m.
15. A pouch type secondary battery, comprising: a battery case
having a pouch shape; a first electrode lead having a first end
within the battery case; a second electrode lead having a first end
electrically connected to a second end of the first electrode lead
and a second end extending outside of the battery case; and a step
compensation part on a side of the second end of the first
electrode lead, wherein a first inclined surface is provided on at
least one of the second end of the first electrode lead and the
first end of the second electrode lead, wherein the step
compensation part includes a plurality of step compensation parts,
wherein the first inclined surface is provided on the other end of
the first electrode lead, and each of the plurality of step
compensation parts has one end contacting the first inclined
surface in a state in which the plurality of step compensation
parts are laminated, and wherein the plurality of step compensation
parts increase in length in order of the lamination to correspond
to an inclined angle of the first inclined surface.
16. The pouch type secondary battery of claim 15, wherein the
battery case includes a first insulating layer and a second
insulating layer configured to seal the battery case around the
first and second electrode leads, wherein the first insulating
layer is bonded to the first electrode lead at a location adjacent
to the electrical connection between the first and second electrode
leads, and wherein the second insulating layer is bonded to the
second electrode lead at a location adjacent to the electrical
connection between the first and second electrode leads.
17. The pouch type secondary battery of claim 16, wherein a bonding
force between the first electrode lead and the first insulating
layer and a bonding force between the second electrode lead and the
second insulating layer are each stronger than a bonding force of
the electrical connection between the first and second electrode
leads.
Description
CROSS-REFERENCE TO RELATED APPLICATION
The present application claims the benefit of the priority of
Korean Patent Application No. 10-2017-0109443, filed on Aug. 29,
2017, which is hereby incorporated by reference in its
entirety.
TECHNICAL FIELD
The present invention relates to a pouch type secondary battery,
and more particularly, to a pouch type secondary battery in which,
when a gas is generated in a case to increase in pressure, a
plurality of electrode leads are reliably attached and detached to
secure complete interruption of an electrical connection.
BACKGROUND ART
Batteries (cells) that generate electric energy through physical or
chemical reaction to supply the generated electric energy to the
outside are used when AC power to be supplied to the building is
not obtained, or DC power is required according to the living
environments surrounded by various electronic devices.
Among such batteries, primary batteries and secondary batteries,
which are chemical cells using chemical reaction, are generally
used. The primary batteries are consumable cells which are
collectively referred to as dry cells. On the other hand, a
secondary battery is a rechargeable battery that is manufactured by
using a material in which oxidation and reduction processes between
current and a material are capable of being repeated many
times.
In general, secondary batteries include nickel-cadmium batteries,
nickel-hydrogen batteries, lithium ion batteries, and lithium ion
polymer batteries. Such a secondary battery is being applied to and
used in small-sized products such as digital cameras, P-DVDs,
MP3Ps, mobile phones, PDAs, portable game devices, power tools,
E-bikes, and the like as well as large-sized products requiring
high power such as electric vehicles and hybrid vehicles, power
storage devices for storing surplus power or renewable energy, and
backup power storage devices.
A lithium secondary battery is generally formed by laminating a
positive electrode (i.e., cathode), a separator, and a negative
electrode (i.e., anode). Also, materials of the positive electrode,
the separator, and the negative electrode may be selected in
consideration of battery lifespan, charging/discharging capacities,
temperature characteristics, stability, and the like. The charging
and discharging of the lithium secondary battery are performed
while lithium ions are intercalated and deintercalated from lithium
metal oxide of the positive electrode to a graphite electrode of
the negative electrode.
In general, unit cells, each of which has a three-layered structure
of a positive electrode/a separator/a negative electrode or a
five-layered structure of a positive electrode/a separator/a
negative electrode/a separator/a positive electrode or a negative
electrode/a separator/a positive electrode/a separator/a negative
electrode, are assembled to constitute one electrode assembly. The
electrode assembly is accommodated in a specific case.
Such a secondary battery is classified into a pouch type secondary
battery and a can type secondary battery according to a material of
a case accommodating the electrode assembly. In the pouch type
secondary battery, an electrode assembly is accommodated in a pouch
made of a flexible polymer material having a variable shape. Also,
in the can type secondary battery, an electrode assembly is
accommodated in a case made of a metal or plastic material having a
predetermined shape.
The secondary battery may be deteriorated in safety due to various
problems such as internal short circuit due to an external impact,
heat generation due to overcharging and overdischarging,
electrolyte decomposition due to the generated heat, and a thermal
runaway phenomenon. Particularly, explosion of the secondary
battery is caused by various causes. For example, an increase in
gas pressure within the secondary battery due to the decomposition
of the electrolyte may also act as one cause.
Particularly, when the secondary battery is repeatedly charged and
discharged, a gas is generated by electrochemical reaction between
the electrolyte and an electrode active material. Here, the
generated gas may allow the secondary battery to increase in
internal pressure to cause problems such as weakening of bonding
force between components, damage of a case of the secondary
battery, an early operation of a protection circuit, deformation of
an electrode, internal short circuit, explosion, and the like.
Thus, in the case of the can type secondary battery, a protection
member such as a CID filter and a safety vent is provided to
physically interrupt an electrical connection when an internal
pressure of a case increases. However, in the case of the pouch
type secondary battery according to the related art, the protection
member is not sufficiently provided.
In recent years, an electrode lead is provided in plurality. Thus,
in the pouch type secondary battery, when the inside of a case is
expanded, technologies for physically interrupting an electrical
connection such as interruption of connection between the plurality
of electrode leads have been proposed. However, in case in which
the connection between the plurality of electrode leads is not
completely interrupted, although the inside of the case is
expanded, electricity may be still be produced from an electrode
assembly and then be supplied to the outside. Thus, since current
is not completely cut off, there is no guarantee that the above
problems are capable of being reliably solved.
DISCLOSURE OF THE INVENTION
Technical Problem
An object of the present invention is to provide a pouch type
secondary battery in which, when a gas is generated in a case to
increase in pressure, a plurality of electrode leads are reliably
attached and detached to secure complete interruption of an
electrical connection.
The objects of the present invention are not limited to the
aforementioned object, but other objects not described herein will
be clearly understood by those skilled in the art from descriptions
below.
Technical Solution
To solve the above problem, a pouch type secondary battery
according to an embodiment of the present invention includes: an
electrode assembly including a positive electrode and a negative
electrode and a separator are laminated; a battery case having a
pouch shape to accommodate the electrode assembly; an electrode tab
connected to the electrode assembly and protruding from one side of
the electrode assembly; a first electrode lead having one end
connected to the electrode tab; a second electrode lead having one
end connected to the other end of the first electrode lead and the
other end protruding to the outside of the battery case; and a
connection part bonding the first electrode lead to the second
electrode lead to connect the first and second electrode leads to
each other, wherein a first inclined surface is provided on at
least one of the other end of the first electrode lead and the one
end of the second electrode lead.
Also, the pouch type secondary battery may further include a step
compensation part disposed on a side of the other end of the first
electrode lead.
Also, the step compensation part may be provided in plurality.
Also, when the first inclined surface is provided on the other end
of the first electrode lead, each of the plurality of step
compensation parts may have one end contacting the first inclined
surface in a state in which the plurality of step compensation
parts are laminated, and the plurality of step compensation parts
may increase in length in order of the lamination to correspond to
an inclined angle of the first inclined surface.
Also, the step compensation part may be integrally provided.
Also, when the first inclined surface is provided on the other end
of the first electrode lead, a second inclined surface may be
provided on one end of the step compensation part.
Also, the second inclined surface may correspond to an inclined
angle of the first inclined surface.
Also, the second inclined surface may contact the first inclined
surface.
Also, the step compensation part may have non-conductivity.
Also, the step compensation part may have a thickness corresponding
to the sum of a thickness of the first electrode lead and a
thickness of the connection part.
Also, the first inclined surface may have an obtuse angle with
respect to a bonding surface on which the first electrode lead and
the second electrode lead are bonded to each other through the
connection part.
Also, the pouch type secondary battery may further include an
insulation part surrounding a portion of each of the first and
second electrode leads to allow the first and second electrode
leads to be bonded to the battery case.
Also, bonding force between each of the first and second electrode
leads and the connection part may be less than that between each of
the first and second electrode leads and the insulation part.
Also, the insulation part may surround a portion at which the first
and second electrode leads are connected to each other through the
connection part.
Also, the insulation part may be made of at least one of
thermoplastic, thermosetting and photocurable resins having
electrical insulation properties.
Also, the connection part may be made of a conductive polymer
including a conductive material.
Also, the connection part may have a thickness of 1 .mu.m to 500
.mu.m.
Particularities of other embodiments are included in the detailed
description and drawings.
Advantageous Effects
The embodiments of the present invention may have at least the
following effects.
Since the first inclined surface is formed on at least one of the
other end of the first electrode lead and one end of the second
electrode lead, the first and second electrode leads may be
reliably detached to secure the complete interruption of the
electrical connection.
In addition, the step compensation part may be disposed on the side
of the other end of the first electrode lead to reduce the height
of the stepped portion, thereby preventing the bonding force
between the insulation part and the electrode lead from decreasing
without increasing in number of processes.
The effects of the prevent invention are not limited by the
aforementioned description, and thus, more varied effects are
involved in this specification.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an assembled view of a pouch type secondary battery
according to an embodiment of the present invention.
FIG. 2 is a perspective view illustrating a state in which the
pouch type secondary battery is completely assembled.
FIG. 3 is a perspective view illustrating a state in which the
pouch type secondary battery is expanded in volume according to an
embodiment of the present invention.
FIG. 4 is a partial cross-sectional view taken along line A-A' of
FIG. 2 in the pouch type secondary battery according to an
embodiment of the present invention.
FIG. 5 is a partial cross-sectional view taken along line A-A' of
FIG. 2 in the state in which the pouch type secondary battery is
expanded in volume according to an embodiment of the present
invention.
FIG. 6 is an enlarged view of a first electrode lead, a second
electrode lead, and a connection part according to the related art
in the state of FIG. 4.
FIG. 7 is an enlarged view of the first electrode lead, the second
electrode lead, and the connection part according to the related
art in the state of FIG. 5.
FIG. 8 is an enlarged view of a first electrode lead, a second
electrode lead, and a connection part in the state of FIG. 4
according to an embodiment of the present invention.
FIG. 9 is an enlarged view of the first electrode lead, the second
electrode lead, and the connection part in the state of FIG. 5
according to an embodiment of the present invention.
FIG. 10 is an enlarged view of a first electrode lead, a second
electrode lead, and a connection part in the state of FIG. 4
according to another embodiment of the present invention.
FIG. 11 is an enlarged view of a first electrode lead, a second
electrode lead, and a connection part in the state of FIG. 4
according to further another embodiment of the present
invention.
FIG. 12 is an enlarged view of a first electrode lead, a second
electrode lead, and a connection part in the state of FIG. 4
according to an additional embodiment of the present invention.
MODE FOR CARRYING OUT THE INVENTION
Advantages and features of the present disclosure, and
implementation methods thereof will be clarified through following
embodiments described with reference to the accompanying drawings.
The present invention may, however be embodied in different forms
and should not be construed as limited to the embodiments set forth
herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the present invention to those skilled in the art.
Further, the present invention is only defined by scopes of claims.
Like reference numerals refer to like elements throughout.
Unless terms used in the present invention are defined differently,
all terms (including technical and scientific terms) used herein
have the same meaning as generally understood by those skilled in
the art. Also, unless defined clearly and apparently in the
description, the terms as defined in a commonly used dictionary are
not ideally or excessively construed as having formal meaning.
In the following description, the technical terms are used only for
explaining a specific exemplary embodiment while not limiting the
inventive concept. In this specification, the terms of a singular
form may comprise plural forms unless specifically mentioned. The
meaning of `comprises" and/or "comprising` does not exclude other
components besides a mentioned component.
Hereinafter, preferred embodiments will be described in detail with
reference to the accompanying drawings.
FIG. 1 is an assembled view of a pouch type secondary battery 1
according to an embodiment of the present invention, and FIG. 2 is
a perspective view illustrating a state in which the pouch type
secondary battery 1 is completely assembled.
In general, in a process of manufacturing a lithium secondary
battery, first, slurry in which an electrode active material, a
binder, and a plasticizer are mixed with each other is applied to a
positive electrode collector and a negative electrode collector to
manufacture a positive electrode plate and a negative electrode
plate. Thereafter, the negative electrode collector and the
positive electrode plate are respectively laminated on both sides
of a separator to form an electrode assembly 10 having a
predetermined shape, and then, the electrode assembly is inserted
into a battery case 13, an electrolyte is injected, and a sealing
process is performed.
As illustrated in FIG. 1, the electrode assembly 10 includes an
electrode tab 11. The electrode tab 11 is connected to each of a
positive electrode and a negative electrode of the electrode
assembly 10 to protrude to the outside of the electrode assembly
10, thereby providing a path, through which electrons moves,
between the inside and outside of the electrode assembly 10. A
collecting plate of the electrode assembly 10 is constituted by a
portion coated with an electrode active material and a distal end,
on which the electrode active material is not applied, i.e., a
non-coating portion. Also, the electrode tab 111 may be formed by
cutting the non-coating portion or by connecting a separate
conductive member to the non-coating portion through ultrasonic
welding. As illustrated in FIG. 1, the electrode tabs 11 may
protrude from one side of the electrode assembly 10 in the same
direction, but the present invention is not limited thereto. For
example, the electrode tabs 11 may protrude in directions different
from each other.
In the electrode assembly 10, the electrode lead 12 is connected to
the electrode tab 11 through spot welding. The electrode lead 12
according to an embodiment of the present invention is provided in
plurality. Also, in the plurality of electrode leads 12, a first
electrode lead (see reference numeral 12a of FIG. 4) is connected
to the electrode tab 11 of the electrode assembly 10, and a second
electrode lead (see reference numeral 12b of FIG. 4) protrudes to
the outside of a battery case 13. The first and second electrode
leads 12a and 12b will be described below in detail. Also, a
portion of the electrode lead 12 is surrounded by an insulation
part 14. The insulation part 14 may be disposed to be limited
within a sealing part, at which an upper pouch 131 and a lower
pouch 132 are thermally fused, so that the electrode lead 12 is
bonded to the battery case 13. Also, electricity generated from the
electrode assembly 10 may be prevented from flowing to the battery
case 13 through the electrode lead 12, and the sealing of the
battery case 13 may be maintained. Thus, the insulation part 14 may
be made of a nonconductor having non-conductivity, which is not
electrically conductive. In general, although an insulation tape
which is easily attached to the electrode lead 12 and has a
relatively thin thickness is mainly used as the insulation part 14,
the present invention is not limited thereto. For example, various
members may be used as the insulation part 14 as long as the
members are capable of insulating the electrode lead 12.
The electrode lead 12 may extend in the same direction or extend in
directions different from each other according to the formation
positions of the positive electrode tab 111 and the negative
electrode tab 112. The positive electrode lead 121 and the negative
electrode lead 122 may be made of materials different from each
other. That is, the positive electrode lead 121 may be made of the
same material as the positive electrode plate, i.e., an aluminum
(Al) material, and the negative electrode lead 122 may be made of
the same material as the negative electrode plate, i.e., a copper
(Cu) material or a copper material coated with nickel (Ni). Also, a
portion of the electrode lead 12, which protrudes to the outside of
the battery case 13, may be provided as a terminal part and
electrically connected to an external terminal.
In the pouch type secondary battery 1, the battery case 13 may be a
pouch made of a flexible material. Also, the battery case 13
accommodates the electrode assembly 10 so that a portion of the
electrode lead 12, i.e., the terminal part is exposed and then is
sealed. As illustrated in FIG. 1, the battery case 13 includes the
upper pouch 131 and the lower pouch 132. A space in which the
electrode assembly 10 is accommodated may be provided in the lower
pouch 132, and upper pouch 131 may be disposed on the space to
cover the space so that the electrode assembly 10 is not separated
to the outside of the battery case 13. As illustrated in FIG. 1,
the upper pouch 131 and the lower pouch 132 may be separately
provided, but the present invention is not limited thereto. For
example, the upper pouch 131 and the lower pouch 132 may be
manufactured through various manners, that is, one side of the
upper pouch 131 and one side of the lower pouch 132 may be
connected to each other.
When the electrode lead 12 is connected to the electrode tab 11 of
the electrode assembly 10, and the insulation part 14 is provided
on a portion of the electrode lead 12, the electrode assembly 10
may be accommodated in the space provided in the lower pouch 132,
and the upper pouch 131 may cover an upper portion of the space.
Also, when the electrolyte is injected, and the sealing part
provided on an edge of each of the upper pouch 131 and the lower
pouch 132 is sealed to manufacture the secondary battery 1 as
illustrated in FIG. 2.
FIG. 3 is a perspective view illustrating a state in which the
pouch type secondary battery 1 is expanded in volume according to
an embodiment of the present invention.
The battery case 13 according to an embodiment of the present
invention may be preferably a pouch made of a flexible material.
Hereinafter, the case in which the battery case 13 is the pouch
will be described.
In general, the battery case 13 accommodating the electrode
assembly 10 includes a gas barrier layer and a sealant layer. The
gas barrier layer blocks introduction and discharge of a gas, and
aluminum (Al) foil is mainly used as the gas barrier layer. The
sealant layer is disposed in the innermost layer and directly
contacts the electrode assembly 10. Also, polypropylene (PP) or the
like is mainly used for the sealant layer. Also, a surface
protection layer may be further provided on an upper portion of the
gas barrier layer. The surface protection layer may be disposed in
the outermost layer and cause friction and collision often with the
outside. Thus, a nylon resin or PET, which mainly has abrasion
resistance and heat resistance, is used for the surface protection
layer.
The pouch type battery case 13 may be manufactured by processing a
film having the above-described lamination structure into the form
of a bag. Thus, when the electrode assembly 10 is accommodated in
the pouch type battery case 13, the electrolyte is injected.
Thereafter, when the upper pouch 131 and the lower pouch 132 may
contact each other, and thermal compression is applied to the
sealing part, the sealant layers may be bonded to each other to
seal the battery case 13. Here, since the sealant layer directly
contacts the electrode assembly 10, the sealant layer may have to
have insulating properties. Also, since the sealant contacts the
electrolyte, the sealant layer may have to have corrosion
resistance. Also, since the inside of the battery case 13 is
completely sealed to prevent materials from moving between the
inside and outside of the battery case 13, high sealability has to
be realized. That is, the sealing part on which the sealant layers
are bonded to each other has to have superior thermal bonding
strength. In general, a polyolefin-based resin such as
polypropylene (PP) or polyethylene (PE) may be used for the sealant
layer. Particularly, polypropylene (PP) is excellent in mechanical
properties such as tensile strength, rigidity, surface hardness,
abrasion resistance, and heat resistance and chemical properties
such as corrosion resistance and thus is mainly used for producing
the sealant layer.
Generally, in the electrode assembly 10, the charging and
discharging are performed by oxidation and reduction reactions.
Here, an electrochemical reaction between the electrolyte and the
electrode active material generates a gas to some degree.
Furthermore, an abnormally more gas may be generated by
overcharging or short-circuiting due to an abnormal reaction in the
electrode assembly 10. However, since all the respective layers are
made of flexible material in the pouch type battery case 13, if the
internal pressure of the battery case 13 increases, the pouch type
secondary battery 1 is expanded in volume as illustrated in FIG. 3.
Recently, techniques in which the electrode lead 12 is provided in
plurality to physically interrupt the electrical connection such as
interruption of the connection between the plurality of electrode
leads 12 when the secondary battery 1 is expanded in volume have
been proposed. However, if the connection between the plurality of
electrode leads 12 is not completely interrupted, electricity is
still produced from the electrode assembly 10, and power is
supplied to the outside. Thus, the above problems may not be surely
solved.
FIG. 4 is a partial cross-sectional view taken along line A-A' of
FIG. 2 in the pouch type secondary battery 1 according to an
embodiment of the present invention.
In the pouch type secondary battery 1 according to an embodiment of
the present invention, as illustrated in FIG. 4, the electrode lead
12 is provided in plurality. That is, the electrode lead 12
includes a first electrode lead 12a connected to the electrode tab
11 of the electrode assembly 10 and a second electrode lead 12b
protruding to the outside of the battery case 13. Also, one surface
of the first electrode lead 12a and one surface of the second
electrode lead 12b are bonded to each other through a connection
part 15 and thus connected to each other.
The connection part 15 connecting the first and second electrode
leads 12a and 12b to each other may have a thin film shape having
conductivity. Particularly, it is preferable that the connection
part 15 has a very thin thickness of 1 .mu.m to 500 .mu.m. Thus,
even though the first and second electrode leads 12a and 12b form a
stepped portion therebetween, a size of the stepped portion may not
be excessively large, and the electricity generated from the
electrode assembly 10 may be easily discharged to the outside. For
this, the connection part 15 may be made of a polymer that is a
conductive material.
The conductive material may include at least one of: natural or
artificial graphite; carbon black such as carbon black, acetylene
black, Ketjen black, channel black, furnace black, lamp black, and
summer black; conductive fiber such as carbon fiber or metal fiber;
metal powders such as carbon fluoride, aluminum, nickel, gold,
silver, and copper powder; powder having a core/shell structure
coated with a different kind of metal on one kind of metal;
conductive whiskey such as zinc oxide and potassium titanate;
conductive metal oxide such as titanium oxide; and conductive
materials such as polyphenylene derivatives.
The polymer may include at least one of an acrylic resin, an epoxy
resin, an ethylene propylene diene monomer (EPDM) resin, a
chlorinated polyethylene (CPE) resin, silicone, polyurethane, an
urea resin, a melamine resin, a phenol resin, an unsaturated ester
resin, polypropylene (PP), polyethylene (PE), polyimide, and
polyamide, and most preferably, an acrylic resin.
As described above, a portion of the electrode lead 12 is
surrounded by the insulation part 14. In a process of sealing the
upper pouch 131 and the lower pouch 132, a relatively high pressure
may be applied to a portion contacting the electrode lead 12 to
damage the sealant layer of the battery case 13. Since the sealant
layer directly contacts the electrode assembly 10 as described
above, the sealant layer may have insulating properties. However,
if the sealant layer is damaged, the electricity may flows to the
battery case 13 through the electrode lead 12. Particularly, since
the gas barrier layer of the battery case 13 is made of a metal
such as aluminum, if the sealant layer is partially damaged to
expose the gas barrier layer, the electricity may easily flow due
to the contact with the electrode lead 12.
Thus, the insulation part 14 may be made of a nonconductor having
non-conductivity, which is not electrically conductive. Also, the
insulation part 14 has high mechanical strength and heat
resistance. Thus, when the upper pouch 131 and the lower pouch 132
are thermally fused, the insulation part 14 may be maintained in
shape to prevent the electrode lead 12 and the gas barrier layer
from contacting each other even through a portion of the sealant
layer is damaged. Thus, the electricity generated from the
electrode assembly 10 may be prevented from flowing to the battery
case 13 through the electrode lead 12. Also, the insulation part 14
has high bonding force. Thus, the insulation part 14 may be
disposed to be limited within a sealing part, at which the upper
pouch 131 and the lower pouch 132 are thermally fused, so that the
electrode lead 12 is bonded to the battery case 13. In general, the
insulating portion 14 may be made of at least one of thermoplastic,
thermosetting and photocurable resins having electrical insulation
properties as a polymer resin. In general, although an insulation
tape which is easily attached to the electrode lead 12 and has a
relatively thin thickness is mainly used as the insulation part 14,
the present invention is not limited thereto. For example, various
members may be used as the insulation part 14 as long as the
members are capable of insulating the electrode lead 12.
As illustrated in FIG. 4, the insulation part 14 may surround all
of the first electrode lead 12a, the connection part 15, and the
second electrode lead 12b. If the first electrode lead 12a or the
connection part 15 is not surrounded by the insulation part 14,
repulsive force may not be applied to the first electrode lead 12a
and the second electrode lead 12b even though the battery case 13
is expanded. The repulsive force will be described below in
detail.
As described below, when the battery case 13 is normal, the first
and second electrode leads 12a and 12b have to be stably connected
to each other. When the secondary battery 13 is expanded, the first
and second electrode leads 12a and 12b have to be easily detached
from each other. Thus, it is preferable that the first and second
electrode leads 12a and 12b are disposed on different planes so
that upper and lower surfaces thereof are connected to each other
instead that the first and second electrode leads 12a and 12b are
disposed on the same plane so that side surfaces thereof are
connected to each other. However, as illustrated in FIG. 4, the
stepped portion may be provided on the portion at which the first
and second electrode leads 12a and 12b are connected to each other,
and thus, the bonding force between the insulation part 14 and the
electrode lead 12 may be reduced. As a result, to reduce the height
of the stepped portion, a step compensation part (see reference
numeral 16 of FIG. 8) is provided. The step compensation part 16
will be described below in detail.
FIG. 5 is a partial cross-sectional view taken along line A-A' of
FIG. 2 in the state in which the pouch type secondary battery is
expanded in volume according to an embodiment of the present
invention.
As described above, when the internal pressure of the pouch type
secondary battery 13 increases, the pouch type secondary battery 1
is expanded in volume. Thus, as illustrated in FIG. 5, an outer
wall of the battery case 13 moves outward. Here, upper and lower
walls of the outer wall of the battery case 13 may have an area
greater than that of the sidewall and be not sealed, resulting in
higher flexibility. Thus, the upper wall of the battery case 13 may
move upward, and the lower wall of the battery case 13 may move
downward.
When the secondary battery 1 is expanded in volume, as illustrated
in FIG. 5, the outer wall of the battery case 13 may move outward
to apply the repulsive force to the first electrode lead 12a and
the second electrode lead 12b through the insulation part 14. Thus,
as the internal pressure of the battery case 13 gradually
increases, the moving force of the outer wall of the battery case
13 may more increase, and the repulsive force applied to the first
electrode lead 12a and the second electrode lead 12b may more
increase. When the bonding force between the first electrode lead
12a and the second electrode lead 12b is greater than the repulsive
force, as illustrated in FIG. 5, the first electrode lead 12a and
the second electrode lead 12b may be detached from each other.
Thus, the electrical connection may be interrupted so that the
electricity does not flow ever. However, the bonding force between
the first and second electrode leads 12a and 12b and the connection
part 15 may be less than that between the first and second
electrode leads 12a and 12b and the insulation part 14. Thus, when
the repulsive force is applied to the first electrode lead 12a and
the second electrode lead 12b, the bonding force between the first
and second electrode leads 12a and 12b and the insulation part 14
may be maintained to maintain the sealing of the battery case 13,
but the first and second electrode leads 12a and 12b may be
detached from each other.
According to an embodiment of the present invention, when the
internal pressure of the battery case 13 increases, the first
electrode lead 12a and the second electrode lead 12b are completely
detected from each other. Also, to completely detach the first and
second leads 12a and 12b from each other, one end of at least one
electrode lead 12 may have a first inclined surface (see reference
numeral 17 of FIG. 8). The first inclined surface 17 will be
described below in detail.
FIG. 6 is an enlarged view of a first electrode lead 120a, a second
electrode lead 120b, and a connection part 15 according to the
related art in the state of FIG. 4, and FIG. 7 is an enlarged view
of the first electrode lead 120a, the second electrode lead 120b,
and the connection part 15 according to the related art in the
state of FIG. 5.
As described above, when a gas is generated in a battery case 13,
an internal pressure of a secondary battery 1 may increase to cause
weakening of bonding force between components, damage of the case
of the secondary battery 1, an early operation of a protection
circuit, deformation of an electrode, internal short circuit,
explosion, and the like. To solve these problems, the electrode
lead 12 includes a first electrode lead 12a connected to an
electrode tab 11 of an electrode assembly 10 and a second electrode
lead 12b protruding to the outside of the battery case 13. Also,
one surface of the first electrode lead 12a and one surface of the
second electrode lead 12b are bonded to each other through a
connection part 15 and thus connected to each other. Here, the
first electrode lead 12a has one end connected to the electrode tab
11 and the other end connected to the second electrode lead 12b.
Also, the second electrode lead 12b has one end connected to the
outer end of the first electrode lead 12a and the other end
protruding to the outside of the battery case 13. Thus, the other
end of the first electrode lead 12a and the one end of the second
electrode lead 12b are connected to each other through a connection
part 15. Also, it is preferable that the first and second electrode
leads 12a and 12b are disposed on different planes so that upper
and lower surfaces thereof are connected to each other.
However, as illustrated in FIG. 6, an inclined surface is not
provided on each of the other end of the first electrode lead 120a
and the one end of the second electrode lead 120b, through which
the first and second electrode leads 120a and 120b are connected to
each other. Thus, when a gas is generated in the battery case 13 to
sufficiently expand the battery case 13, the first and second
electrode leads 120a and 120b have to be completely detected from
each other. However, as illustrated in FIG. 7, the other end of the
first electrode lead 120a is still in contact with the second
electrode lead 120b. If the connection between the plurality of
electrode leads 12 is not completely interrupted, electricity is
still produced from the electrode assembly 10, and power is
supplied to the outside. Thus, the above problems may not be surely
solved.
FIG. 8 is an enlarged view of a first electrode lead 12a, a second
electrode lead 12b, and a connection part 15 in the state of FIG. 4
according to an embodiment of the present invention, and FIG. 9 is
an enlarged view of the first electrode lead 12a, the second
electrode lead 12b, and the connection part 15 in the state of FIG.
5 according to an embodiment of the present invention.
As illustrated in FIG. 8, the other end of the first electrode lead
12a according to an embodiment of the present invention includes a
first inclined surface 17. Here, the first inclined surface 17 may
have an obtuse angle with respect to the bonding surface on which
the first electrode lead 12a is bonded to the first electrode lead
12b through the connection part 15. That is, the bonding surface of
the first electrode lead 12a may have a length greater than an
opposite surface that is disposed at an opposite side and connected
to the insulation part 14. Thus, when the internal pressure of the
battery case 13 increases to be expanded, as illustrated in FIG. 9,
the second electrode lead 12b may be bent outward to reliably
detach the first and second electrode leads 12a and 12b from each
other (here, the `detach` may mean that an adsorbed or attached
part is separated). That is, the complete interruption of the
electrical connection between the first and second electrode leads
12a and 12b may be secured. On the other hand, an opposite surface
of the bonding surface may have a length greater than that of the
bonding surface. Thus, the bonding force between the first
electrode lead 12a and the insulation part 14 may not be
significantly reduced.
As described above, when the battery case 13 is normal, the first
and second electrode leads 12a and 12b have to be stably connected
to each other to stably supply the electricity generated from the
electrode assembly 10 to the outside. On the other hand, when the
battery case 13 is expanded, the first and second electrode leads
12a and 12b have to be easily detached from each other to interrupt
the electrical connection therebetween. Thus, it is preferable that
the first and second electrode leads 12a and 12b are disposed on
different planes so that upper and lower surfaces thereof are
connected to each other instead that the first and second electrode
leads 12a and 12b are disposed on the same plane so that side
surfaces thereof are connected to each other.
However, a stepped portion may be provided at a portion, at which
the first and second electrode leads 12a and 12b are connected to
each other, by a difference in thickness between the first and
second electrode leads 12a and 12b even though the connection part
15 has a thin thickness. However, the insulation part 14 may
include the portion at which the first and second electrode leads
12a and 12b are connected to each other to surround a portion of
the electrode lead 12. Here, the bonding force between the
insulation part 14 and the electrode lead 12 may be reduced by the
formed stepped portion. As a result, the sealing of the battery
case 13 may not be maintained, and thus, the electrolyte injected
into the battery case 13 may leak to the outside. To solve this
problem, a technique of performing the sealing process twice while
surrounding the portion, at which the stepped portion is formed, by
the insulation part 14 is proposed. Thus, since the process is
performed twice, the process may be cumbersome and increase in
number.
Thus, according to an embodiment of the present invention, as
illustrated in FIG. 8, to reduce the height of the stepped portion,
a step compensation part 16 is provided at a side of the other side
of the first electrode lead 12a. When the step compensation part 16
is provided in plurality, all the step compensation parts 16a and
16b are laminated in parallel to each other. Also, the laminated
step compensation parts 16 may have a thickness corresponding to
the sum of a thickness of the first electrode lead 12a and a
thickness of the connection part 15. Here, it is preferable that
the correspondence means that the thickness of the step
compensation part 16 is the same as the sum of the thickness of the
first electrode lead 12a and the thickness of the connection part
15. Also, even though there is some difference in thickness in the
process, the correspondence may mean that the difference is within
an error range to minimally reduce the height of the stepped
portion.
As described above, the step compensation part 16 may be disposed
at a side of the other end of the first electrode lead 12a to
reduce the height of the stepped portion, thereby reducing the
bonding force between the insulation part 14 and the electrode lead
12 without increasing in number of processes.
Here, to prevent a gap from being generated between the step
compensation part 16 and the first electrode lead 12a, it is
preferable that the step compensation part 16 contacts the other
end of the first electrode lead 12a. If the step compensation parts
16a and 16b are provided in plurality, and the first inclined
surface 17 is formed on the other end of the first electrode lead
12a, as illustrated in FIG. 8, one end of each of the step
compensation parts 16a and 16b contacts the first inclined surface
17 while the step compensation parts 16a and 16b are laminated.
Also, the plurality of step compensation parts 16a and 16b may have
lengths that gradually increase in an order of the lamination
thereof with respect to an inclined angle of the first inclined
surface 17. That is, it is preferable that one end of one of the
plurality of step compensation parts 16a and 16b protrudes from one
end of the other one to form a stepped shape, and all the other
ends of the step compensation parts 16a and 16b are disposed on the
same plane.
To prevent the electricity transmitted from the first electrode
lead 12a from leaking to the outside, it is preferable that the
step compensation part 16 is made of a nonconductor having
non-conductivity, which is not electrically conductive.
FIG. 10 is an enlarged view of a first electrode lead 12a, a second
electrode lead 12b, and a connection part 15 in the state of FIG. 4
according to another embodiment of the present invention.
The step compensation parts 16a and 16b according to an embodiment
of the present invention are provided in plurality so as to be
laminated, and an end of each of the step compensation parts 16a
and 16b contacts a first inclined surface 17 provided on the other
end of the first electrode lead 12a. However, since the inclined
surface is not provided on each of the step compensation parts 16a
and 16b, in the plurality of step compensation parts 16a and 16b,
one end of each of the step compensation parts 16a and 16b further
protrudes than the other end to form a stair shape. However,
according to another embodiment of the present invention, a second
inclined surface 18 is provided on one end of each of a plurality
of step compensation parts 16c and 16d. Also, the second inclined
surfaces 18 of the step compensation parts 16c and 16d have the
same inclined angle, and the inclined angle of each of the second
inclined surface 18 corresponds to the inclined angle of the first
inclined surface 17. Here, it is preferable that the correspondence
means that the inclined angle of the second inclined surface 18 is
the same as that of the first inclined surface 17, but the
difference is within an error range even though some difference in
angle occurs. Thus, as illustrated in FIG. 11, when the step
compensation part 16 is disposed on the same plane as the first
electrode 12a at a side of the other end of the first electrode
lead 12a, it is preferable that the first inclined surface 17
provided on the other end of the first electrode lead 12a and the
second inclined surface 18 provided on one end of the step
compensation part 16 come into surface contact with each other, but
not come into line contact with each other. Thus, even though one
end of one of the plurality of step compensation parts 16c and 16d
further protrudes than one end of the other of the plurality of
step compensation parts 16c and 16d, the second inclined surfaces
18 may have the same plane shape, but do not have the stair shape.
Thus, the gap between the first electrode lead 12a and the step
compensation part 16 may be more reduced to reduce possibility of
separation of the step compensation part 16.
FIG. 11 is an enlarged view of a first electrode lead 12a, a second
electrode lead 12b, and a connection part 15 in the state of FIG. 4
according to further another embodiment of the present
invention.
A step compensation part 16e according to further another
embodiment of the present invention may not be provided in
plurality but provided to be integrated as one step compensation
part 16e. Thus, since it is unnecessary to perform a process of
laminating the step compensation part 16, the number of processes
may be reduced. Also, when the second inclined surfaces 18 are
provided, since it is unnecessary to adjust the second inclined
surfaces 18 to be disposed at the same plane, the manufacturing
process may be more simplified, and also, an occurrence of a defect
rate may be reduced. That is, according to various embodiments of
the present invention, although the step compensation part 16 is
provided in plurality, the present invention is not limited
thereto. For example, only one step compensation part 16 may be
provided.
FIG. 12 is an enlarged view of a first electrode lead 12c, a second
electrode lead 12d, and a connection part 15 in the state of FIG. 4
according to an additional embodiment of the present invention.
As described above, the other end of the first electrode lead 12a
according to an embodiment of the present invention includes the
first inclined surface 17. However, according to further another
embodiment of the present invention, the first electrode lead 12c
does not include the first inclined surface 17a. On the other hand,
as illustrated in FIG. 12, one end of the second electrode lead 12d
includes the first inclined surface 17a. Here, the first inclined
surface 17a may have an obtuse angle with respect to the bonding
surface on which the second electrode lead 12d is bonded to the
first electrode lead 12c through the connection part 15. That is,
the bonding surface of the second electrode lead 12d may have a
length greater than an opposite surface that is disposed at an
opposite side and connected to the insulation part 14.
When the battery case 13 is expanded, as illustrated in FIG. 9, the
second electrode lead 12b is bent outward. However, as illustrated
in FIG. 5, the first electrode lead 12a may bent outward. Here, one
end of the second electrode lead 12d may include the first inclined
surface 17a to more facilitate complete detachment of the first and
second electrode leads 12c and 12d.
Furthermore, although not shown, all of the other end of the first
electrode lead 12a and one end of the second electrode lead 12b may
include the first inclined surfaces 12, respectively. Furthermore,
although not shown, all of the other end of the first electrode
lead 12a and one end of the second electrode lead 12b may include
the first inclined surfaces 12, respectively.
According to further another embodiment of the present invention,
since the other end of the first electrode lead 12c does not
include the first inclined surface 17a, it is preferable that the
second inclined surface 18 is not provided on the step compensation
part 16. Thus, as illustrated in FIG. 12, although step
compensation parts 16f and 12g are provided in plurality, the
plurality of step compensation parts 16f and 16g may have the same
length. Thus, one end of each of the plurality of step compensation
pats 16f and 16g may contact the other end of the first electrode
lead 12c, and thus, the gap may not be generated. As a result, the
bonding force between the first electrode lead 12c, the step
compensation part 16, and the insulation part 14 may not be
deteriorated.
Those with ordinary skill in the technical field of the present
invention pertains will be understood that the present invention
can be carried out in other specific forms without changing the
technical idea or essential features. Therefore, the
above-disclosed embodiments are to be considered illustrative and
not restrictive. Accordingly, the scope of the present invention is
defined by the appended claims rather than the foregoing
description and the exemplary embodiments described therein.
Various modifications made within the meaning of an equivalent of
the claims of the invention and within the claims are to be
regarded to be in the scope of the present invention.
* * * * *